Buy article online - an online subscription or single-article purchase is required to access this article.
Download citation
Download citation
link to html
The title compound, C11H10N3+·Cl-·H2O, belongs to the N1-methyl-substituted imidazo­[4,5-f]­quinoline family, in which the heterocyclic ring is protonated at the pyridine rather than at the imidazole N atom. The mol­ecule as a whole is almost exactly planar. The molecular structure has been compared with that of the 2-amino analogue described in the literature, and it was found that the extra amino group of the latter is involved in conjugation with the adjacent double bond, i.e. the conjugation does not extend over the entire heterocyclic system. The cation of the title compound forms a strong hydrogen bond with the Cl- anion and the anions are interconnected by the water solvent mol­ecule.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102008089/sk1549sup1.cif
Contains datablocks global, II

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270102008089/sk1549IIsup2.hkl
Contains datablock II

CCDC reference: 188629

Comment top

Imidazoquinolines, produced in cooked meats, have long been known as strong mutagens and carcinogens (Nagao et al., 1977; Weissberger & Taylor, 1981). On the other hand, in the last few years some derivatives incorporating the imidazoquinoline nucleus have been reported to possess antimutagenic/antitumour activity (Lankaputhra & Shah, 1998; Bishop et al., 2001). It is obvious that the mutagenicity/antimutagenicity depends sensitively on the substitution pattern of the imidazoquinoline nucleus; for example, 2-amino-3-methylimidazo[4,5-f]quinolines are typical mutagens, while removal of the 2-amino group and substitution on the pyridine-fused ring promotes antimutagenic activity. It is, however, unclear whether the influence of the substituents reflects their effect on the charge distribution of the heterocyclic ring (and hence determines the orientation of the molecule in the DNA intercalation site) or results from interaction of the substituents with minor groove functionalities of DNA. Thus, detailed information on the three-dimensional and electronic structures of these heterocycles is indispensable for an analysis of structure-function relationships.

Though highly important, there have been only a few reports on these subjects. Of the electronic characteristics, only protonation, tautomerization and valence tautomerism of selected imidazo[4,5-f]quinolines have been studied using theoretical methods in the past few years (Ögretir & Kaniskan, 1993; Milata, 2001).

Similarly, as revealed by a search of the Cambridge Structural Database (CSD, Version?; Allen & Kennard, 1993), only one crystal structure of the imidazo[4,5-f]quinoline family, namely 2-amino-3-methylimidazo[4,5-f]quinoline, (I) (Yokoyama et al., 1980), has so far been reported. Consequently, the present crystal structure determination was undertaken in order to establish the precise molecular dimensions (bond lengths) of another derivative, the title compound, (II), which is a deamino isomerically methylated analogue of (I), as the chloride monohydrate. \sch

The asymmetric part of the unit cell of (II) consists of a protonated molecule of 1-methyl-1H-imidazo[5,4-f]quinoline, one Cl- anion and one water molecule. A perspective view of the cation, along with the atom-numbering scheme, is shown in Fig. 1. The molecule as a whole (i.e. including the exocyclic methyl group) is planar within the limits of experimental error [r.m.s. deviation 0.025 (4) Å].

As can be seen in Fig.1, the first protonation has taken place at the pyridine atom N6 rather than at the imidazole N atom; this is in line with the theoretical calculations, which predicted the energy difference between the two protonated forms to be 8.7 kcal mol-1 (1 kcal mol-1 = 4.184 kJ mol-1; Ögretir & Kaniskan, 1993).

As mentioned above, the main purpose of this work was to compare the molecular dimensions of the present derivative, (II), with its 2-amino analogue, (I), in order to shed more light on the relationship between the structure and (anti)mutagenic properties of compounds incorporating the imidazoquinoline heterocycle. This comparison has shown that the corresponding bond lengths in the two molecules are equal to within experimental error, except for the C2—N3 bond distance, which is 0.035 (5) Å shorter in (II) than in (I), obviously due to conjugation of the lone pair electrons on the amine N atom with the adjacent double bond in (I). Thus, as judged from the distribution of bond lengths in molecules (I) and (II), the conjugation in (I) does not extend beyond the CN double bond of the heterocyclic system. This means that the large difference in pharmacological properties between (I) and (II) lies in the interaction of the additional amino group with DNA functionalities, and not in the effect of the amino group on the π-electron distribution of the heterocyclic π system. These results will form the basis for subsequent quantum chemical calculations of the electronic structure and molecular modelling (docking) studies of DNA-ligand interactions.

The positive charge of the protonated molecule in (II) is neutralized by the Cl- anion, which is involved in a hydrogen bond with N6+—H [for N6—H···Cl, N6—H 0.86 Å, H···Cl 2.20 Å, N···Cl 3.060 (4) Å and N—H···Cl 177°]. The molecule of water of crystallization forms two rather weak hydrogen bonds to symmetrically related Cl- ions. Apart from these hydrogen-bond interactions, there are no other contacts substantially shorter than the sum of the van der Waals radii of the atoms concerned.

Experimental top

A stirred solution of 9-chloro-1-methyl-1H-imidazo[5,4-f]quinoline (0.35 g, 1.5 mmol), prepared previously (Milata, 2001), and solid NaOH (0.15 g) was hydrogenated at 120 kPa on Raney nickel until the theoretical amount of hydrogen (60 ml) was consumed. The catalyst was filtered off, and the filtrate was neutralized with 10% HCl and purified by column chromatography (silica gel, chloroform-methanol 10:1). Crystallization from ethanol-water (2:1) afforded the title compound, (II) (yield 40%, m.p. 601–603 K).

Refinement top

Although all the H atoms were seen in a difference Fourier map, they were refined with fixed geometry (C—H = 0.93–0.96 Å and N—H = 0.86 Å) riding on their carrier atoms, with Uiso(H) set to 1.2 (1.5 for the methyl H atoms) times Ueq of the parent atom, except for the water H atoms, the coordinates of which were kept fixed at their experimentally found values, with Uiso equal to 1.2Ueq of the O(W) atom.

Computing details top

Data collection: Syntex software (Syntex, 1973); cell refinement: Syntex software; data reduction: XP21 (Pavelčík, 1987); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. A view of the cation of (II) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 35% probability level and H atoms are shown as small circles of arbitrary radii.
1-Methyl-1H-imidazo[5,4-f]quinolin-6-ium chloride monohydrate top
Crystal data top
C11H10N3+·Cl·H2OZ = 2
Mr = 237.69F(000) = 248
Triclinic, P1Dx = 1.448 Mg m3
Dm = 1.45 (1) Mg m3
Dm measured by flotation in bromoform/c-hexane
Hall symbol: -P 1Melting point: 602 K
a = 7.544 (5) ÅMo Kα radiation, λ = 0.71073 Å
b = 9.084 (6) ÅCell parameters from 15 reflections
c = 9.152 (8) Åθ = 8–22°
α = 72.65 (6)°µ = 0.33 mm1
β = 66.61 (5)°T = 293 K
γ = 76.96 (7)°Prism, colourless
V = 545.3 (7) Å30.35 × 0.30 × 0.20 mm
Data collection top
Syntex P21
diffractometer
Rint = 0.000
Radiation source: fine-focus sealed tubeθmax = 27.6°, θmin = 2.4°
Graphite monochromatorh = 09
θ/2θ scansk = 1111
2511 measured reflectionsl = 1011
2511 independent reflections2 standard reflections every 98 reflections
1197 reflections with I > 2σ(I) intensity decay: 2%
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.070Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.201H atoms treated by a mixture of independent and constrained refinement
S = 0.92 w = 1/[σ2(Fo2) + (0.1128P)2]
where P = (Fo2 + 2Fc2)/3
2511 reflections(Δ/σ)max = 0.002
146 parametersΔρmax = 0.34 e Å3
0 restraintsΔρmin = 0.44 e Å3
Crystal data top
C11H10N3+·Cl·H2Oγ = 76.96 (7)°
Mr = 237.69V = 545.3 (7) Å3
Triclinic, P1Z = 2
a = 7.544 (5) ÅMo Kα radiation
b = 9.084 (6) ŵ = 0.33 mm1
c = 9.152 (8) ÅT = 293 K
α = 72.65 (6)°0.35 × 0.30 × 0.20 mm
β = 66.61 (5)°
Data collection top
Syntex P21
diffractometer
Rint = 0.000
2511 measured reflections2 standard reflections every 98 reflections
2511 independent reflections intensity decay: 2%
1197 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0700 restraints
wR(F2) = 0.201H atoms treated by a mixture of independent and constrained refinement
S = 0.92Δρmax = 0.34 e Å3
2511 reflectionsΔρmin = 0.44 e Å3
146 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.0186 (5)0.3262 (4)1.2599 (4)0.0416 (8)
C10.0797 (7)0.4649 (5)1.1981 (5)0.0516 (11)
H1A0.01010.54751.27850.077*
H1B0.21680.49421.17530.077*
H1C0.05290.44561.09940.077*
C20.1204 (6)0.3133 (6)1.4065 (5)0.0509 (11)
H20.18920.39481.47890.061*
N30.1499 (5)0.1772 (5)1.4376 (4)0.0522 (10)
C40.0093 (6)0.0611 (5)1.2689 (5)0.0476 (11)
H40.06000.12051.34570.057*
C50.1396 (6)0.1237 (5)1.1234 (5)0.0420 (10)
H50.16040.22661.09990.050*
N60.3736 (5)0.0998 (4)0.8600 (4)0.0409 (8)
H60.38780.19580.84140.049*
C70.4771 (6)0.0241 (5)0.7462 (5)0.0462 (10)
H70.56160.07540.64760.055*
C80.4630 (6)0.1304 (5)0.7697 (5)0.0479 (11)
H80.53740.18360.68830.057*
C90.3384 (6)0.2035 (5)0.9142 (5)0.0402 (9)
H90.32920.30830.93250.048*
C100.0204 (5)0.0939 (5)1.3028 (5)0.0381 (9)
C110.2439 (5)0.0340 (4)1.0074 (5)0.0383 (9)
C120.2238 (5)0.1231 (4)1.0360 (4)0.0342 (9)
C130.0850 (5)0.1829 (4)1.1890 (5)0.0351 (9)
Cl0.43405 (18)0.43774 (13)0.80011 (14)0.0563 (4)
W0.3008 (5)0.6826 (4)0.5189 (4)0.0737 (11)
H1W0.37500.63000.43400.110*
H2W0.33500.60500.60300.110*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0397 (18)0.049 (2)0.0349 (18)0.0092 (15)0.0120 (15)0.0062 (15)
C10.058 (3)0.043 (2)0.050 (3)0.014 (2)0.018 (2)0.001 (2)
C20.038 (2)0.066 (3)0.042 (2)0.008 (2)0.0124 (19)0.004 (2)
N30.046 (2)0.069 (3)0.0365 (19)0.0080 (19)0.0100 (17)0.0122 (18)
C40.049 (3)0.055 (3)0.045 (2)0.006 (2)0.019 (2)0.026 (2)
C50.044 (2)0.040 (2)0.049 (2)0.0063 (18)0.022 (2)0.0129 (19)
N60.0433 (19)0.0377 (18)0.0437 (19)0.0109 (15)0.0199 (16)0.0019 (15)
C70.040 (2)0.054 (3)0.040 (2)0.012 (2)0.0113 (19)0.003 (2)
C80.040 (2)0.060 (3)0.043 (2)0.003 (2)0.012 (2)0.018 (2)
C90.041 (2)0.040 (2)0.043 (2)0.0054 (18)0.0155 (19)0.0124 (17)
C100.037 (2)0.049 (2)0.034 (2)0.0016 (18)0.0192 (17)0.0112 (18)
C110.035 (2)0.045 (2)0.040 (2)0.0058 (17)0.0192 (18)0.0084 (18)
C120.034 (2)0.041 (2)0.034 (2)0.0046 (16)0.0195 (17)0.0078 (17)
C130.033 (2)0.040 (2)0.038 (2)0.0061 (16)0.0179 (17)0.0087 (16)
Cl0.0733 (8)0.0456 (6)0.0580 (7)0.0087 (5)0.0298 (6)0.0135 (5)
W0.076 (2)0.059 (2)0.065 (2)0.0032 (18)0.0143 (19)0.0075 (17)
Geometric parameters (Å, º) top
N1—C21.355 (5)N6—C71.307 (5)
N1—C131.378 (5)N6—C111.367 (5)
N1—C11.441 (5)N6—H60.8600
C1—H1A0.9600C7—C81.377 (6)
C1—H1B0.9600C7—H70.9300
C1—H1C0.9600C8—C91.358 (6)
C2—N31.302 (6)C8—H80.9300
C2—H20.9300C9—C121.400 (5)
N3—C101.367 (5)C9—H90.9300
C4—C51.351 (6)C10—C131.387 (5)
C4—C101.399 (6)C11—C121.404 (5)
C4—H40.9300C12—C131.411 (5)
C5—C111.405 (5)W—H1W0.9488
C5—H50.9300W—H2W0.9530
C2—N1—C13105.6 (4)N6—C7—C8121.1 (4)
C2—N1—C1125.1 (4)N6—C7—H7119.4
C13—N1—C1129.3 (3)C8—C7—H7119.4
N1—C1—H1A109.5C9—C8—C7118.7 (4)
N1—C1—H1B109.5C9—C8—H8120.7
H1A—C1—H1B109.5C7—C8—H8120.7
N1—C1—H1C109.5C8—C9—C12120.8 (4)
H1A—C1—H1C109.5C8—C9—H9119.6
H1B—C1—H1C109.5C12—C9—H9119.6
N3—C2—N1114.4 (4)N3—C10—C13110.9 (4)
N3—C2—H2122.8N3—C10—C4128.8 (4)
N1—C2—H2122.8C13—C10—C4120.3 (4)
C2—N3—C10104.0 (3)N6—C11—C12117.5 (4)
C5—C4—C10119.3 (4)N6—C11—C5119.5 (4)
C5—C4—H4120.4C12—C11—C5123.0 (4)
C10—C4—H4120.4C9—C12—C11118.6 (4)
C4—C5—C11120.3 (4)C9—C12—C13126.8 (4)
C4—C5—H5119.8C11—C12—C13114.6 (3)
C11—C5—H5119.8N1—C13—C10105.0 (3)
C7—N6—C11123.2 (4)N1—C13—C12132.5 (4)
C7—N6—H6118.4C10—C13—C12122.5 (4)
C11—N6—H6118.4H1W—W—H2W95.6
C13—N1—C2—N30.3 (5)N6—C11—C12—C90.8 (5)
C1—N1—C2—N3179.2 (4)C5—C11—C12—C9178.2 (4)
N1—C2—N3—C100.5 (5)N6—C11—C12—C13178.8 (3)
C10—C4—C5—C110.1 (6)C5—C11—C12—C132.2 (5)
C11—N6—C7—C81.0 (6)C2—N1—C13—C100.9 (4)
N6—C7—C8—C90.2 (6)C1—N1—C13—C10178.5 (4)
C7—C8—C9—C121.1 (6)C2—N1—C13—C12177.9 (4)
C2—N3—C10—C131.1 (5)C1—N1—C13—C122.8 (7)
C2—N3—C10—C4178.8 (4)N3—C10—C13—N11.2 (4)
C5—C4—C10—N3176.7 (4)C4—C10—C13—N1179.2 (4)
C5—C4—C10—C130.9 (6)N3—C10—C13—C12177.7 (3)
C7—N6—C11—C120.5 (6)C4—C10—C13—C120.3 (6)
C7—N6—C11—C5179.5 (4)C9—C12—C13—N12.2 (7)
C4—C5—C11—N6179.3 (4)C11—C12—C13—N1177.4 (4)
C4—C5—C11—C121.7 (6)C9—C12—C13—C10179.3 (4)
C8—C9—C12—C111.6 (6)C11—C12—C13—C101.1 (5)
C8—C9—C12—C13178.0 (4)

Experimental details

Crystal data
Chemical formulaC11H10N3+·Cl·H2O
Mr237.69
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)7.544 (5), 9.084 (6), 9.152 (8)
α, β, γ (°)72.65 (6), 66.61 (5), 76.96 (7)
V3)545.3 (7)
Z2
Radiation typeMo Kα
µ (mm1)0.33
Crystal size (mm)0.35 × 0.30 × 0.20
Data collection
DiffractometerSyntex P21
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
2511, 2511, 1197
Rint0.000
(sin θ/λ)max1)0.651
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.070, 0.201, 0.92
No. of reflections2511
No. of parameters146
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.34, 0.44

Computer programs: Syntex software (Syntex, 1973), Syntex software, XP21 (Pavelčík, 1987), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson, 1976), SHELXL97.

Selected geometric parameters (Å, º) top
N1—C21.355 (5)N6—C71.307 (5)
N1—C131.378 (5)N6—C111.367 (5)
N1—C11.441 (5)C7—C81.377 (6)
C2—N31.302 (6)C8—C91.358 (6)
N3—C101.367 (5)C9—C121.400 (5)
C4—C51.351 (6)C10—C131.387 (5)
C4—C101.399 (6)C11—C121.404 (5)
C5—C111.405 (5)C12—C131.411 (5)
C2—N1—C13105.6 (4)N3—C10—C4128.8 (4)
C2—N1—C1125.1 (4)C13—C10—C4120.3 (4)
C13—N1—C1129.3 (3)N6—C11—C12117.5 (4)
N3—C2—N1114.4 (4)N6—C11—C5119.5 (4)
C2—N3—C10104.0 (3)C12—C11—C5123.0 (4)
C5—C4—C10119.3 (4)C9—C12—C11118.6 (4)
C4—C5—C11120.3 (4)C9—C12—C13126.8 (4)
C7—N6—C11123.2 (4)C11—C12—C13114.6 (3)
N6—C7—C8121.1 (4)N1—C13—C10105.0 (3)
C9—C8—C7118.7 (4)N1—C13—C12132.5 (4)
C8—C9—C12120.8 (4)C10—C13—C12122.5 (4)
N3—C10—C13110.9 (4)
 

Subscribe to Acta Crystallographica Section C: Structural Chemistry

The full text of this article is available to subscribers to the journal.

If you have already registered and are using a computer listed in your registration details, please email support@iucr.org for assistance.

Buy online

You may purchase this article in PDF and/or HTML formats. For purchasers in the European Community who do not have a VAT number, VAT will be added at the local rate. Payments to the IUCr are handled by WorldPay, who will accept payment by credit card in several currencies. To purchase the article, please complete the form below (fields marked * are required), and then click on `Continue'.
E-mail address* 
Repeat e-mail address* 
(for error checking) 

Format*   PDF (US $40)
   HTML (US $40)
   PDF+HTML (US $50)
In order for VAT to be shown for your country javascript needs to be enabled.

VAT number 
(non-UK EC countries only) 
Country* 
 

Terms and conditions of use
Contact us

Follow Acta Cryst. C
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds